Luminaire



March 24, 1970 G. E. MULVEY ETAL 3,502,860

' LUMINAIRE Filed Dec. 4, 1967 2 Sheets-Sheet 1 LENS BRIGHTNESS FOOTLAM BERTS LENS WIDTH INCHES FIG 3 INVENTORS GERARD E. MULVEY GEORGE EZOAKE March 24, 1970 G. E. MULVEY ETAL 3,502,860

LUMINAIRE Filed Dec. 4, 1967 v 2 Sheets-Sheet 2 TRANSVERSE 6 LONGITUDINAL amsumsss FOOTLAMBERTS 0| 8| 0 O as so 15 10 as so 55 so 45 FIG 4 Z r 7 Q0 4 2o 4 2 4 1222a FIG 7b FIG 70 INVENTORS GERARD E. MULVEY GEORGE E. BOAKE BY g mwn United States Patent US. Cl. 2409 8 Claims ABSTRACT OF THE DISCLOSURE A luminaire of the type usually employed in false ceilings in which the lenses may be recessed with relation to the plane of the ceiling to provide an improved and more attractive appearance, and in which the depth of the notfer boxes is substantially reduced without impairing the efficiency of the operation of the fluorescent lamps inside. The lenses are of substantially greater area, and therefore a reduced brightness, may be employed without the development of unsightly dark patches in the lenses. The luminaires may be associated with air handling facilities or may be employed without any apparent change to the naked eye. The luminaires essentially comprise a basic trofler box assembly of certain predetermined lengths, width and depth in relation to the length, and number, of the lamps themself. The troffer boxes are associated with separate supporting frames to which they are attached by a concealed flange. The frames are adapted to incorporate the air handling facilities in an advantageous manner.

This invention relates to luminaires having increased lighting efficiency, reduced brightness characteristics, and adapted for attachment with air handling facilities.

Current building practises particularly for oflice and institutional construction, require working areas for personnel to be illuminated to a certain predetermined minimum level, but at the same time, place certain restrictions upon the brightness characteristics of the source of illumination while such source is within the normal field of vision of personnel. For example, a recommended building practise lays down maximum brightness characteristics which may not be exceeded running from a minimum at an angle of about 85 from the perpendicular to a maximum at about 45 to the perpendicular. For the purposes of these standards, brightness characteristics between 45, and the perpendicular, i.e., directly beneath the light source are not generally speaking subject to restriction since it is assumed that personnel will not be looking directly at the light source within that arc.

The achievement of adequate lighting level, without exceeding such brightness characteristics, employing standard lamp tubes and diffuser lenses, does not itself present any serious problem. All that is required is to provide a mounting for the tubes sufiiciently far distant from lenses or diffusers of a sufficiently great area so that the lens or diffuser which is all that will be seen by the naked eye will not appear to be excessively bright at any one point, while nevertheless transmitting sufficient quantity of light to provide adequate illumination. However, the I design of buildings, particularly office construction, places increasingly strict limitations on the amount of space available between the false ceiling and the poured concrete floor immediately above it such that it is seldom possible for the lighting fixtures to be provided with adequate space between the tubes and the lenses so as to achieve the desired result. Thus it becomes necessary, due to the limitation of space within the building design, to place the lamps too close to the lenses with a result that parts of the lenses appear excessively bright,'and other parts appear, by contrast to be dark. Such a result will generally violate the building practise, and at the same time provide an unattractive appearance which detracts from the appearance of the building. This problem becomes particularly appravated when it is attempted to incorporate air handling facilities with the lighting fixtures, as is becoming increasingly popular in attempts to eliminate unattractive air diffusers and return grilles. Such air handling facilities, when combined with light troffers, usually comprises a series of slotted openings arranged along each side of the light troffer formed in flanges incorporated in the sheet metal construction of the troffer itself. Due to the design of the ceiling modules in many cases, the space required for such slotted openings cannot always be provided by merely extending the width of the troffers outwardly. In the majority of cases in fact, it has been necessary to reduce the width of the lenses in order to provide room for the incorporation of such slotted openings. Obviously, the reduced width of the lenses leads to a still further increase in brightness within the critical arc, which in the majority of cases can only be overcome by reducing the efllciency of the tube. In addition, the reduction in width of the lenses has usually been accompanied by a reduction in the volume of the light trofier boxes themselves which has lead to a further problem. Thus the conventional lamps operate a maximum efliciency and over their greatest life when maintained within a certain predetermined narrow temperature range. The problem of maintaining a stable predetermined temperature range is greatly aggravated when the contained volume of the high troffer is reduced and as a result, in some cases, attempts have been made to incorporate air flow openings within the traffic itself. However, this leads to very great fluctuations in temperature since the rate of heat loss of the tubes cannot be controlled and there is a consequent loss in efficiency and lamp life.

In addition, it is considered desirable by architects and interior designers to provide a ceiling construction, and particularly to provide lighting fixtures in the ceiling construction which embody what is known as a dynamic appearance. Thus lighting fixtures which incorporate a lens arranged flush with the ceiling present a flat unvarying appearance no matter from which direction it is viewed. On the other hand, a lighting fixture in which the lens is recessed within the ceiling is immediately more attractive and interesting to the eye since its appearance varies depending upon the direction from which it is viewed. Obviously, in view of the factors mentioned above, the provision of a recessed lens within the ceiling still further reduces the spacing available between the lamps and the lens and also reduces the contained volume of the light troffer still further. Thus it has not generally been considered feasible to provide recess lighting fixtures of this type, notwithstanding their obvious aesthetic appeal.

The diffuser lenses which are usually employed in these types of lighting fixtures consist of, in the majority of cases, sheets of acrylic plastic one side of which is moulded in predetermined pattern of angled prismatic surfaces whereby to diffuse light passing therethrough. The si-mplest kind of lens consists merely of a sheet of such material testing on the lips around the lower edge of the light troffer. In this type of lens, the inherent weight of the plastic material will cause the lens to deflect out of shape if it is attempted to span too great a space with the lens. This problem can be overcome by providing a lens having, for example, a rigid metal frame, or still further by moulding a criss-cross pattern of bracing ribs in the material for example, and other expedients have been employed in the past. However, any such lens which con sists of more than a simple flat sheet of plastic material must necessarily cost considerably more, which especially in the case of office construction where many hundreds of light trotfers and lenses will be employed, adds significantly to the cost of the lighting installation. In addition, such fabricated composite lenses may become broken or disfigured in use and a stock of such lenses must be maintained over a considerable period of time in order to provide for replacement over the life of the building at least. Obviously, this problem will not occur where the lens is a simple sheet of plastic which can be cut to any desired size.

In the past, the size of the light troffers has generally speaking been determined by the standard sizes of lamps made available by the tube manufacturers. Thus in the majority of cases, four foot tubes are employed in lighting fixtures in false ceiling in office and institutional constructions, eight foot tubes being usually confined to use in commercial and industrial locations. In the majority of cases therefore the light troffers have been designed to be of about four feet in length and either two feet or four feet in width depending upon the number of tubes employed. Where a four foot ceiling module is employed for the design of the ceiling, supported for example on ceiling Ts arranged in a criss-cross pattern four feet square, then the loaction and support of four foot troffers presents little or no problem. However, it is usually considered desirable to arrange light troifers in continuous lines end to end for maximum lighting efiiciency. If a four foot troffer is used in a four foot ceiling module then the light troffers will be butted end to end with only about one or one and a half inches between ends. This narrow spacing in turn causes problems when it is attempted to erect partitions in the space. Building partitions are usually between two and six inches in width, and they will be therefore unable to pass between the ends of two adjacent troffers, and the partition is bound to overlap one or other troffers. As a result, the partitions of buildings usually require the substitution of standard troifers with non-standard troifers of special design so as to avoid such overlapping. One solution is the use of a ceiling module greater than the length of the troffers. Thus if a five foot module is used with four foot trotfers then the problem of erecting partitions is solved. However, in the case, a new problem arises namely the support of the troffers themselves. Since the grid of ceiling TS in this case will be on five foot squares or rectangles having one side five foot in length, a troffer only four feet long must necessarily be supported by some other means. thereby involving further expense in providing such supporting means and requiring much greater time for erection. In addition, it then becomes necessary to provide specially cut non-standard sections of acoustic ceiling material to fill in the gap between the four foot troffer and the five foot ceiling Ts. The use of a troffer designed especially for the particular ceiling module of any particular building would of course answer this problem. However, conventional techniques call for trotfers constructed of sheet metal, and the die costs involved in designing a special trolfer for each building would make this solution highly uneconomic since the die costs would have to be amortised over a very short production run.

The invention seeks to provide as a general objective, a luminaire having greatly increased lighting efliciency by providing a stable operating temperature within the troffer, a realtively low profile trotfer to fit within a minimum spacing between the ceiling and the floor above, a trofier designed particularly adapted for use with recessed lenses, and with lenses of greater area than in prior art troffers and in which any local shadow areas in the lens are concealed or avoided, and which is particularly adapted for use in conjunction with air handling systems.

More particularly, the invention seeks to provide a luminaire having the foregoing advantages in which the sheet metal light troffer may be of standard uniform design while being provided with a simple supporting framework which may readily be modified to suit variations in the ceiling module dimensions.

More particularly, it is an objective of the present invention to provide a light troffer having the foregoing advantages in which lenses are employed of greater overall area, of simple economical construction, and in which sagging or deflection of the lenses is avoided or eliminated completely.

More particularly, it is an objective of the present invention to provide a luminaire having the foregoing advantages in which the light troffer is provided with a greater contained volume, without impairing the attachment of air handling facilities, and without requiring greater spacing between the ceiling and the floor.

More particularly, it is an objective of the present invention to provide a light trofier having the foregoing advantages in which air handling facilities can be incorporated, and air handling delivery and return slots may be provided without any reduction in the width of the lenses and without in any way detracting from the appearance of the luminaires themselves.

The foregoing and other objectives will become apparent from the following description of a preferred embodiment of the invention which is given here by way of example only with reference to the following views and diagrams in which like reference devices refer to like parts thereof throughout various views and diagrams and in which;

FIGURE 1 is a perspective illustration of a luminaire troffer shown erected in position in a false ceiling, the ceiling construction being partially broken away for clar- FIGURE 2 is a section along the line 2-2 of FIGURE 1 showing air handling facilities attached to the light trotfer;

FIGURE 3 is brightness distribution curve showing the brightness of the lenses when viewed from beneath;

FIGURE 4 is a brightness variation curve showing the increase in brightness of the lenses as the viewing angle changes from to 45;

FIGURE 5 is a section along the line 5-5 of FIG- URE 1;

FIGURE 6 is a greatly enlarged section along the line 66 of FIGURE 1, and,

FIGURES 7A and 7B are sections corresponding to FIGURE 6 showing alternative embodiments for use in different forms of ceiling construction.

From FIGURES 1 and 2 it will be noted that these illustrations show a conventional form of ceiling construction comprising a criss-cross network of supporting Ts 1 supported at intervals by wires 2 and providing support for ceiling tiles 3. In this embodiment, the basic ceiling module is five feet square, each module being filled by two tiles 1 of five feet long by eighteen inches wide, and between them a luminaire five feet long by two feet wide, although, obviously other forms of ceiling modules may be accommodated according to the practise of the present invention without departing from the scope of the invention.

The luminaire according to the invention will be seen to comprise two main portions namely the trotfer box indicated as 10 and the trofier frame indicated generally as 11. The box 10 consists essentially of rectangular sheet metal construction having a top portion 12 side walls 13 and end walls 14. In this embodiment, two lamps indicated as L are connected between respective electrical fixtures 15. An intermediate light bafiie 16 is provided along the median portion of top 12 extending lengthwise between tubes L. Endwise light baffles 17 are provided at each end of trotfer box 10 angled downwardly from the top within baffle 16. It will be appreciated that the electrical cables and connections have been omitted from this illustration for the sake of clarity, but they will obviously be connected between ballast B and lighting fixtures 15, being concealed from View by the baffle members l6 and 17. It will be noted that in this embodiment the ceiling module, as stated, is five feet by five feet, and

the trofier box is so dimensioned as to take maximum advantage of these dimensions. Thus the width dimension of troffer box 10 is almost equal to the two foot spacing between ceiling Ts 10 in the one direction, and in the other direction, is about four or five inches shorter than the 'full five foot spacing. In accordance with generally accepted electrical engineering standards, it would normally have been thought necessary, in a troifer of approximately two feet in width, to provide a spacing between the tubes and the lens of the troifer of somewhere in the region of six or seven inches in order to provide even light distribution across the lens. However, as will become apparent herein, the spacing in very considerably reduced by the practice of the invention.

It will be noted that, in the trolfer box 10, its lower side as defined by the lower most peripheries of side walls 13 and end walls 1 4 is completely open and free of any obstruction, and is provided with outwardly extending supporting flanges 18 and 19 for attachment to the frame 11.

In order to rigidify and support troifer box 10, frame 11 is constructed separately therefrom of rigid girder like members formed, in this preferred embodiment of continuous aluminum extrusions welded together thus achieving a strong rigid supporting structure at very low cost the appearance and dimensions of which may readily be varied without major tooling changes, and also which may be adapted for connection to air handling facilities without in any way changing the appearance, all as will be described below.

Thus frame 11 comprises frame side members 20 frame end members 21 and at least one frame intermediate member 22. Frame side member 20 is illustrated in enlarged section in FIGURE 6 and will be seen to comprise a generally inverted rectangular channel shaped section having inward and outward channel side wall members 23 and 24 and an intermediate channel top wall 25, the lower most edges of channel walls 23 and 24 defining an open mouth indicated as 26. In order to provide for attachment to side wall 13 of troffer box 10, an upwardly extending attachment flange member 27 is formed along the upper side of channel top wall thereby permitting such attachment by means of, for example, self tapping screws 28 without interfering with the appearance of channel top wall 25. In order to interengage with ceiling Ts 1, a horizontal supporting rib 29 is formed along the outer surface of channel outer wall 24, spaced above the lower periphery thereof by a distance equal to the thickness of ceiling Ts 1 thereby to support the same in a common plane.

Frame end members 21 are illustrated in section in FIGURE 5. They will be seen to comprise inner and outer channel side walls 30 and 31 and channel top wall 32 defining three sides of a rectangular channel, with the lower peripheries of side walls 30 and 31 defining an open mouth 33. An upwardly extending flange member 34 is provided along the upper side of top member 32 for means to be described hereinafter. It will be noted that member 34 on end member 21 is somewhat lower in profile than member 27 on side members 20, since generally speaking no attachment of the troffer box 10 is required at this point.

The dimensions of side members 20 are preferably such that the rectangular frame defined by sides 20 and end member 21 is somewhat shorter than the spacing between the ceiling Ts 1, and in order to fill the space between same, and to provide for endwise support of the frame 11, extension member 35 is formed along the lower periphery of outer wall 31 of end member 21 and is supported at its outer periphery by means of horizontally extending support flange 36 offset from the plane of extension member 35 by an amount equal to the thickness of ceiling T 1 whereby to locate the lower surface of extension member 35 in the same plane as ceiling T 1. End member 21 and side members 20 are joined at the corners of the frame by mitred corners and welding around the upwardly directed surfaces thereof, whereby to provide a frame having appearance from below characterized by a continuous deep rectangular shaped channel.

In order to provide additional strength and support, frame 11 includes one or more intermediate members 22, illustrated in FIGURE 2, of identical section with that of side members 20 with the exception that support flange 29 is omitted whereby to provide a uniform appearance on each side thereof. Intermediate member 22 is joined at each end to end member 22.

Due to the increased width of the trolfer 12 in relation to prior art troffers, two lenses 37 are provided formed of sheet acrylic material cut in rectangular form so as to lie and be supported on the upper surfaces of side members 20 end members 21 and intermediate members 22 of frame 11, being located in position by ribs 27 and 34 thereof as shown.

If it is desired to provide air handling facility in association with luminaires according to the invention, this may readily be achieved by forming slotted openings 38 in the outer walls 24 of side members 20 of frame 11. In this case, air handling ducts indicated generally as D in FIGURE 2 may be connected thereto, or, more simply, the space between the false ceiling and the floor above may be divided by party walls into air delivery and return plenums according to well known practice, whereby the need for connecting individual ducts D to each of the luminaires is avoided.

By the practice of the invention, luminaires may be provided having trofler boxes of very considerable width and of a length greater than the length of the fluorescent lamps which they contain thereby providing a contained volume or air space which is sufficient to ensure that a stable working temperature is maintained within lamps L. By the same means, lenses 37 may be employed which are of greater length than lamps L and are of greater width than would normally be regarded as desirable in relation to the spacing of lenses 37 from lamps L. Thus, with reference to FIGURE 3, the distribution of brightness across lenses 37 is shown, and it will be noted that the brightness drops off sharply at each side of lenses 37 and also along a median zone, thus resulting in an undesirable darkening or shadow effect along such median zone. This is overcome by the use of the intermediate frame member 22 located precisely along such median zone which effectively distracts the eye from the shadow and enhances the overall appearance. In addition, the use of intermediate member 22 makes it possible to employ a very much larger lens area than in the past, without the need to employ a specially supported lens, lenses 37 being merely cut from sheet acrylic material, the support provided by the frame and the intermediate frame member 22 in particular, being sufficient notwithstanding the fact that lenses 37 are both of greater length than lamps L and also span a greater width than in the past.

In addition, the use of such lenses 37 having a greater area than in the past, makes it possible to employ fluorescent lamps L of a greater efficiency and light output than would normally be regarded as desirable, without producing a resultant increase in brightness of the lens when viewed directly from an angle, by reason of the fact that the greater quantity of light is distributed over a greater lens area. In fact, the brightness variation of the lens 37 of luminaires according to the invention appears substantially as shown in FIGURE 4, varying only gradually from the extreme viewing angle to the 45 viewing angle, which curves are well within accepted building practices.

Furthermore, by reason of the use of a troifer box 10 which is substantially shorter than the spacing between the ceiling T 1, and a troifer frame 11 which is formed separately from box 10 of excluded material, it becomes possible to provide for minor variations within the dimensions of the ceiling by merely shortening the troffer frame 11, without altering the troffer box 10. In addition, it is of course possible to provide various sizes of luminaires based upon lamps of two foot or three foot lengths, for special locations, while maintaining the same uniform appearance as provided by the frame 11, without being obliged to employ a large number of different dies. When used with air handling facilities, or when used without air handling, the appearance of luminaires according to the invention will remain uniform and unchanged, and it will be difiicult if not impossible for persons viewing the luminaires, at least when they are lighted, to determine or locate the presence of the air handling slots 38. The concealment of such slots 38 will also produce a further advantage in that the discolouration and dust accumulation which usually collects around such air handling opening over a period of time will be hidden of concealed within the darkened channel of side mem bers 20.

It will be appreciated that the design of the troffer frame 11 may be subject to wide variations, depending for example upon the dimensions of the ceiling module, and in some cases upon the type of ceiling construction. Thus for example, a ceiling of conventional plaster construction in which there is not predetermined module, will require various changes in the design, and the length of the luminaires will be largely dependant upon the taste of the architect. In addition, it will be appreciated that while in the presently preferred embodiment, the luminaires are shown suported on the ceiling Ts themselves, the light troffers may be supported by wires or other means from the joists of the floor above, or may be supported between ceiling Ts or other ceiling supporting members of other designs such as H members or L shaped members, or by means or yokes or braces extending between ceiling members and extending over or around the troffer boxes 10.

Two possible alternative embodiments are illustrated in FIGURES 7A and 7B. In FIGURE 7A, there is illustrated a design suitable for use with a ceiling constructed of tile members which must abut against the frame, with air handling openings located in the top wall portion of the channel if desired. In FIGURE 7B, there is illustrated a further design for producing a different appearance having one horizontally directed channel beside the lenses which may for example be coloured as by anodizing in various different colours, and another downwardly oriented channel which is provided with an upwardly angled flange to make a flush joint with a plaster ceiling, and the air handling opening in this case is illustrated as being partly in the outer side wall and partly in the top wall member. Obviously, many other variations in the r section of the stock used in forming the frame 11 may be employed without departing from the spirit of the invention.

The foregoing is a description of the preferred embodiment and of the invention which is given here by way of example only. The invention is not to be taken as limited to any of the specific features described, but comprehend all such variations as come within the spirit and scope of the appended claims.

What we claim is:

1. A luminaire lighting fixture for use in association with false ceilings, for accommodating fluorescent lamps of a predetermined length L in feet, said luminaire comprising;

a troifer box unit having side and end walls defining an open lower side for containing fluorescent lamps; lamp connection fixture in said box for supporting lamps therein in predetermined location;

a separate rigid integral supporting frame permanently attached in fixed location to said side walls of said box around said open lower side thereof;

said frame comprising side and end members joined at right angles and formed from stock defining an upwardly extending recessed channel in section which is continuous around said side and end walls and having parallel inner and outer side Walls and a top wall said frame being dimensioned to locate portions of said top walls of said frame side and end members in inwardly overlapping relation to said troffer box side walls; upwardly directed troffer attachment means on said frame side members at least fastened to said troifer box side walls, said attachment means being located in intermediate relation to the planes of said frame inner and outer side Walls whereby to locate said frame side members with portions of said top walls in inwardly overlapping relation as aforesaid, and,

lens supporting surfaces on said inwardly overlapping to wall portions for supporting lens means upwardly recessed within said frame in predetermined location with respect to the location of said lamps in said box thereby ensuring maximum lens open area for passage of light therethrough while permitting the spacing between the location of said lamps and said lens to be reduced.

2. A luminaire as claimed in claim 1 wherein said troffer box is formed of sheet metal construction, and said support frame is formed of extruded metal stock cut to length and formed into an integral rigid frame, said frame forming the exterior visible portion of said luminaire, and said box being attached to said frame by means concealed from view.

3. A luminaire as claimed in claim 1 wherein said frame and said box are of unequal length.

4. A luminaire as claimed in claim 1 including at least one surface on said inner walls of said frame members adjacent to said lens and visible when said luminaire is installed, said surface being directly illuminated by light radiated from said lens and being located to prevent direct illumination of said upwardly extending channel thereby.

5. A luminaire as claimed in claim 1 including slotted air handling openings formed in said frame side members, said openings being located within and concealed by said channel.

6. A luminaire as claimed in claim 1 including supporting rib means formed along the outer side walls of said frame side members at least for supporting said luminaire in said ceiling.

7. A luminaire as claimed in claim 1 including extension members on said frame end members.

8. A luminaire as claimed in claim 1 wherein said lighting fixture incorporates two lenses and including a further intermediate frame member extending between said frame end members midway therealong and defining in section the same upwardly extending channel as said frame side and end members, whereby to provide intermediate lens support means permitting said lenses to be supported side by side.

References Cited UNITED STATES PATENTS 2,846,569 8/1958 Frizzell et al. 3,103,868 9/1963 Kodaras. 3,154,001 10/1964 Zurawski. 3,190,208 6/1965 Styne et al. 3,193,001 7/1965 Meckler. 3,246,137 4/1966 Zagel. 3,383,811 5/1968 Ades 5228 FOREIGN PATENTS 705,764 3/ 1965 Canada.

NORTON ANSHER, Primary Examiner R. L. MOSES, Assistant Examiner US. Cl. X.R. 

